1. Field of the Invention
The present invention relates to a variable venturi carburetor to be installed in an internal combustion engine for automobiles.
2. Description of the Prior Art
In recent years, the automotive industry has continually exerted efforts to meet the governmentally imposed standards on exhaust emissions and to increase the fuel economy of automotive engines. One of these efforts includes to develop such technology as to run an engine stably with a relatively lean fuel-air mixture and a low idle engine speed. The prior art in trying to meet the above requirements has employed an idle and low speed system in addition to a main metering system for a fuel passage in a variable venturi carburetor. According to this prior art, the air-fuel ratio in a variable venturi carburetor is controlled by altering an annular area defined between a main jet and a metering needle. The problems associated with this type of carburetor include that it is sometimes difficult for the main jet and the metering needle which control air-fuel ratio to respond quickly to a change in the fuel flow rate in the idle and low speed system. Furthermore, there arises another problem that it is costly to install an idle and low speed system in a variable venturi carburetor.